Comerica (CMA) 8-K Other Events

Exhibit 12.1

Computation of Ratios of Earnings to Fixed Charges

	Three months ended March 31,						For the year ended December 31,
(dollars in millions)	2018			2017			2017			2016			2015			2014			2013 (a)
Earnings:
Income before income taxes	$	335		$	268		$	1,234		$	670		$	750		$	870		$	786
Less:
Interest and penalties on tax liabilities		—			—			4			3			1			(4	)		(1	)
Income before income taxes after interest on tax liabilities		335			268			1,230			667			749			874			787
Plus:
Fixed charges		47			31			144			135			118			122			136
Earnings, including interest on deposits		382			299			1,374			802			867			996			923
Less:
Interest on deposits		16			9			42			40			43			45			55
Earnings, excluding interest on deposits	$	366		$	290		$	1,332		$	762		$	824		$	951		$	868
Fixed charges:
Interest expense	$	41		$	26		$	121		$	112		$	95		$	95		$	112
Interest portion of rental expense		6			6			23			23			23			27			24
Total fixed charges		47			32			144			135			118			122			136
Less:
Interest on deposits		16			9			42			40			43			45			55
Total fixed charges, excluding interest on deposits	$	31		$	23		$	102		$	95		$	75		$	77		$	81
Earnings to fixed charges:
Excluding interest on deposits		11.75	x		12.90	x		13.03	x		7.94	x		10.87	x		12.42	x		10.73	x
Including interest on deposits		8.06	x		9.38	x		9.53	x		5.94	x		7.31	x		8.21	x		6.81	x

(a) Prior period balances have been adjusted for the Q1 2014 adoption of ASU2014-01.